Hydroxyalkylation of cellulose and derivatives



Patented Sept. 19, 19-39 UNITED STATES PATENT OFFICE Aubrey Ernest Broderick,

South Charleston, W.

Va., assi nor to Carbide and Carbon Chemicals Corporation, a corporation of New York No Drawing; Application December 2, 1937, Serial No. 177,759

4 Ulaims.- (Cl. 260-231) This invention relates to a process for the vapor-phase catalytic hydroxyalkylation of cel-' tial or complete esteriiication, and or derivatives readily peptiaable in dilute caustic soda solutions for the preparation oi shaped objects, as well as-ior the hydroxyalkylation 01 paper stock prior to the formation of the.

web and calendered sheet to increase its absorbency. It also is applicable to the-hydroxyalkylation of flax, hemp, ramie, and cotton yarns to alter their chemical properties, such as susceptibility to dyeing agents, wetting-out agents, etc., without altering other than to increase its softness.

In the practice of the invention, alr,-dry cellulose,i.,e., cel.ulose containing from 2% to 10% of moisture,is reacted with the vapor of an alkylene oxide, such ,as ethylene oxide and propylene oxide, in the presence of a tertiary amine that is also in the vapor-phase,the reactions being conducted'preierably at atmospheric pressure or subatmospheric pressure.

The reaction is so conducted that not substantially more than 30% of the alkylene oxide is combined with the cellulose. Temperatures are employed ranging from atmospheric temperature to around 0.; and particularly suitable are those within the range from 45 to 60 C.

The tertiary amine is employed in amounts ranging from around to 10% of the air-dry cellulose, and preferably in amounts of not more than 1%. Among tertiary amines suitable as catalysts in the process may be mentioned pyridine, l-methyl pyrrol, tripropyl amine, triethyl amine, and trimethyl amine.

The vaporized tertiary amine may be introduced and contacted with the cellulose in several ways. For example, the autoclave containing the cellulose may be evacuated and the required amount oi amine vapor allowed to flow in immediately prior to introduction of the alkylene oxide vapor; or the amine vapor may be contacted with the cellulose after contacting the latter with a small portion of the alkylene oxide vapor; or the two vaporous materials may be concurrently added slowly and proportionately to the cellulose.

films, filaments and other the physical term of the yarn The first-named method is preierred. The amine vapor also may be passed through the cellulose and absorbed by the fibers up to the desired concentration prior to introduction of the alkylene oxide, although if the amine is absorbed by the cellulose to very large extent,--upon subsequent addition of the alkylene oxide, a portion of the latter is converted to aldehyde, which resiniiles. This is particularly true when employing trimethyl amine.

The cellulose employed may be any of th usual commercial types. It is also possible to employ in the process neutral cellulose that has been previously depolymerized by treatment with mineral acid or the equivalent; and cellulose derivatives such as partially etherified or esterifled celluloses which have some free hydroxyl groups.

In the preferred practice of the invention the cellulose material, such as cotton linters, which material preferably is in a highly fluiled state, is agitated or tumbled in a rotating jacketed autoclave which has been evacuated to remove the air. The alkylene oxide vapor is fed continuously into the rotating autoclave,-the flow thereoi being adjusted to. regulate the rate of the reaction and control the fluid presure within the autocave. The catalysts may be introduced into the cellulose material either before or during flow of the alkylene oxide. The absence of appreciable dilution of the alkylene oxide vapor with air in the autoclave facilitates the hydroxyalkylation oi the celluiose and prevents appreciable formation of oxycellulose in the presence of the catalyst. The rate of addition of the alkylene oin'de vapor to the celluloslc material is regulated by a valve to approximately the rate at which it reacts with the cellulose material,-and so that the pressure within the autoclave never substantialy exceeds that of the atmosphere. As a result of this slow addition of the alkylene oxide, it has been found that, when ethylene oxide is used as the hydroxyalkylating agent, the maximum amount of ethylene oxide vapor present at any time in the autoclave under atmospheric pressure at 50 C. is around 3% of the weight of the air-dry cellulose. In operations at lower pressures, this proportion desirably is increased somewhat. The reaction is completed when all of the oxide vapor introduced has reacted with the cellulose, so that the subatmospheric pressure secured by the original evacuation oi? the autoclave is approximately reached again. The resultant mass of etherifled cellulose'then is removed, and may be stored in that condition, or may be readily purified by extraction with warm water, centrifuged and dried.

Example 1 100 grams of fluffy alpha wood pulp containing approximately 6% of moisture were introduced into an autoclave having an inside volume of 11.1

liters. After evacuating the autoclave to an absolute pressure of 4 mm. of mercury, 24 grams of ethylene oxide vapor and 9.312 gram of trirncthyl amine vapor were simultaneously introduced over a period of ii] to $2 hours while tumbling the autoclave and heating at as until a pressure oi approximately 22 .6 min. oi mercury absolute was obtained. The resultant stheriilcd cellulose was removed and, after formly etherified hydroxyethyi cellulose which was practically insoluble in caustic soda even upon freezing, but was acetylated by the dope method very much more readily than the original cellulose material used as starting material.

Eramplc 2 100 grams of loosely-finned cotton linters were introduced into the autoclave described in Example 1. After evacuation of the autoclave, 2 grams of pyridine vapor were introduced during agitation. Thereafter, 30 grams of propylene oxide vapor were slowly introduced into the autoclave over a period of 15 hours, during agitation thereof, while maintaining the contents at around 60 C. The heating and agitation were continued until a. pressure of approximately 500 mm. of mercury absolute was secured in the autoclave. The resultant product, after extraction with warm water, yielded 108.4 grams of hydroxypropyl cellulose containing 8.4% of combined propylene oxide, and having properties similar to the product of Example 1 as to insolubility in dilute caustic alkali solutions and reactivity with acetylatlng agents.

Example 3 420 grams of loosely-fiufled, air-dry. low-viscosity alpha wood pulp, previously depolymerized with dilute sulfuric acid. were placed in a 5- gallon tumbling autoclave. the latter evacuated to a pressure of about 500 mm. of mercury absolute, and a small portion (about of a total charge of 109 grams of ethylene oxide vapor was introduced therein. Thereafter, 5.68 grams of trimethyl amine vapor were introduced, following which the balance of the ethylene oxide vapor was slowly added over a period of 5 hours. After 11 hours of tumbling and heating at 50 C., the original pressure of 500 mm. of mercury absolute obtained by the evacuation was again attained. and the reaction discontinued. The resultant etheriflcation product was slightly pink in color, and showed a. gain oi 26.9% based upon the weight of the original alpha pulp.

It was substantially completely soluble in a dilute aqueous solution of caustic alkali yielding a i satire Example 4 Following the procedure described in Example 2, 1 gram of triethyl amine was introduced into a tumbling autoclave and mixed with 100 grams of alpha wood pulp. After securing in the autoclave a vacuum of 711.2 mm. of mercury absolute at 30 C., 20 grams of ethylene oxide vapors then were introduced over a period of 24 hours, during agitation of the mixture and while maintaining the same at around 60 C. At the end of 20 hours the autoclave pressure had fallen to 330.2 mm. of mercury absolute at the latter temperature. The resultant reaction product, hydroxyeihyl cellulose, contained 4.3 grams of combined ethylene oxide based upon the original weight of the alpha. pulp. It was substantially insoluble in dilute caustic alkali solutions, but is acctyluted more readily than the alpha pulp sturtin material.

Eramplc 5 To 55.3 grams of fibrous hydroxyethyl cellulose acetate, containin 23.6% of combined acetic acid and around 0.5% to 1% of moisture, was added water in amount sufiiclent to bring the moisture content of the mixtuie to approximately 8%. (The said hydroxyethyl cellulose acetate was prepared by reacting cotton iinters with of its weight of ethylene oxide followed by acetylation of the resultant hydroxycthyl cellulose ether at to 25 C., with an excess of acetic anhydride in the presence 01' sulfuric acid, using isopropyl acetate as a diluent. Thc aforesaid fibrous hydroxyethyl cellulose was removed from the acetylating mixture at. the end of 4 hours purposely so as to obtain only a partially acetyiatcd product.)

The diluted ester was placed in a 5-gallon container which was then evacuated. Thereupon 3.5 grams of pyridine were vaporized and conducted into the container and mixed with the diluted ester. 13.5 grams of ethylene oxide vapor were then slowly flowed into the container and the contents of the latter were aaltated at C. for 24 hours. The resultant product was thoroughly extracted with water to remove the pyridine and excess ethylene oxide. The washed product after drying at 70 C. for 24 hours weighed 59.9 grams and had a combined acetic acid content of 13.7%.

The practice of the present invention offers important advantages in instances where it is cellulose in the presence of some car ier for the hydroxyalkylating agent or catalyst, such as water or a. liquid organic diluent. The absence of diluents permits a more rapid and uniform reaction between the alkylene oxide and cellulose, and minimizes the amount of catalyst necessary to permit completion of the reaction under the mild hydroxyalkylating conditions. This 0bviates, too, the necessity for recovery of a liquid carrier. Purification of the final product is not necessary in most instances, as the amount of catalyst present is extremely small; and the mildness of the treatment prevents or minimizes the formation 01' any substantial amounts of undesirable cellulose depolymerization products. The readiness with which the etherifled celluloses of the present invention may be purified is noteworthy. Because of the low aikylene oxide content oi the products, made possible by the use of prodabsorbent than products of the usual high alkylene oxide content. and which yield films ing higher wet strengths than the latter. The use oi low reaction temperatures within the temperature range named inhibits or prevents polymerization losses of the alkylene oxide and improves the emciency or the process.

The term "a cellulose is employed in the claims to designate not only more or less pure celluloses such as alpha wood pulp. suiflte wood pulp (rayon grades), cotton linters and the like, but also cellulose derivatives such as partially etherified or esterifled celiuloses having therein one or more free hydroxyl groups.

The invention is susceptible of modification within the scope or the appended claims.

I claim:

1. Process for the hydromalkyiation of a cellulose, which comprises contacting a stream oi vapors or an alkylene oxide with a cellulose, in the presence or a tertiary amine catalyst in the vapor-phase within a zone under subatmospheric pressure, and regulating the rate of introduction or the alkylene oxide to the said cellulose in accordance with the rate of reaction between said cellulose and said alkylene oxide, to prevent the pressure in the said zone from rising substantially above atmospheric pressure.

2. Process for the hydroflaikylation or a cellulose which comprises slowly introducing a CERTIFICATE OF Patent No 2,175 L 70 ond column, line 11,

sure;

AUBREY ERNEST stream oi vapors of an alkylene oxide into a cellulose within a zone under subatmospheric pressure maintained at a temperature within the range from around atmospheric to around 60 C.,

the alkylene oxide to prevent said zone from atmospheric pressure, the total amount of alkylene oxide introduced into the said zone being between 1% and 30% of the weight of the cellulose.

3. Process for the pressure in the the hydroxyalkylation of a cellulose, which comprises subjecting an agitated 30% or the weight of the cellulose, and recovering the hydroxyalkylated cellulose thus produced.

4. Process as defined in claim 3 wherein the alkylene oxide employed is ethylene wherein the maximum ethylene oxide in contact any time constitutes a few percent 0! the latter.

AUBREY ERNEST BR01788108- EORRECTION.

September 19, 1959.

BRODERICK.

It is hereby certified that error appear-sin the printed specification of the above numbered patent requiring correction as follows: Page 1, secline ET, for "increased" for "th" read the;

read decreased;

line 26, for "presure" read presand that the said Letters Patent shouldbe read with this correction therein that the same may conform to the record of the case in the Signed and sealed this 17th (Seal) i Patent Office day of October, A. D. 1959.

Henry Van Arsdale, Acting Commissioner of Ifatents.

cl introduction of rising substantially above around at which it and the total amount thus contacted being less than oxide, and amount or uncombined with the cellulose at a of the mm worthy. Because of the low aikylene oxide content oi the products, made possible by the use of prodabsorbent than products of the usual high alkylene oxide content. and which yield films ing higher wet strengths than the latter. The use oi low reaction temperatures within the temperature range named inhibits or prevents polymerization losses of the alkylene oxide and improves the emciency or the process.

The term "a cellulose is employed in the claims to designate not only more or less pure celluloses such as alpha wood pulp. suiflte wood pulp (rayon grades), cotton linters and the like, but also cellulose derivatives such as partially etherified or esterifled celiuloses having therein one or more free hydroxyl groups.

The invention is susceptible of modification within the scope or the appended claims.

I claim:

1. Process for the hydromalkyiation of a cellulose, which comprises contacting a stream oi vapors or an alkylene oxide with a cellulose, in the presence or a tertiary amine catalyst in the vapor-phase within a zone under subatmospheric pressure, and regulating the rate of introduction or the alkylene oxide to the said cellulose in accordance with the rate of reaction between said cellulose and said alkylene oxide, to prevent the pressure in the said zone from rising substantially above atmospheric pressure.

2. Process for the hydroflaikylation or a cellulose which comprises slowly introducing a CERTIFICATE OF Patent No 2,175 L 70 ond column, line 11,

sure;

AUBREY ERNEST stream oi vapors of an alkylene oxide into a cellulose within a zone under subatmospheric pressure maintained at a temperature within the range from around atmospheric to around 60 C.,

the alkylene oxide to prevent said zone from atmospheric pressure, the total amount of alkylene oxide introduced into the said zone being between 1% and 30% of the weight of the cellulose.

3. Process for the pressure in the the hydroxyalkylation of a cellulose, which comprises subjecting an agitated 30% or the weight of the cellulose, and recovering the hydroxyalkylated cellulose thus produced.

4. Process as defined in claim 3 wherein the alkylene oxide employed is ethylene wherein the maximum ethylene oxide in contact any time constitutes a few percent 0! the latter.

AUBREY ERNEST BR01788108- EORRECTION.

September 19, 1959.

BRODERICK.

It is hereby certified that error appear-sin the printed specification of the above numbered patent requiring correction as follows: Page 1, secline ET, for "increased" for "th" read the;

read decreased;

line 26, for "presure" read presand that the said Letters Patent shouldbe read with this correction therein that the same may conform to the record of the case in the Signed and sealed this 17th (Seal) i Patent Office day of October, A. D. 1959.

Henry Van Arsdale, Acting Commissioner of Ifatents.

cl introduction of rising substantially above around at which it and the total amount thus contacted being less than oxide, and amount or uncombined with the cellulose at a of the mm 

